SCELSE research on electrochemically active biofilms (EABs) has been featured on the cover of Biointerphases journal.
EABs can be potentially used in applications such as wastewater treatment and bioelectrosynthesis of high value products.
Currently EAB structure and activity are studied using flat electrodes, but three-dimensional (3D) electrodes provide a higher surface area to volume ratio which allows for more electrical interaction between bacteria and electrode, and are thus more suitable for large-scale applications.
To investigate this, SCELSE researchers selected a type of material called carbon veil (CV) which is useful as an anode because of its flexibility, low cost, high porosity and high mechanical strength. Eight pieces of thin CV were overlapped to create a complex 3D carbonaceous electrode.
They chose Shewanella oneidensis MR-1 as the model EAB forming microbe because it can transfer electrons in both anodic and cathodic extracellular electron transfer. For biofilm imaging, they used confocal laser scanning microscopy (CLSM) because it is non-destructive, requires minimal pre-treatment and can produce a very high image resolution.
Their results showed that biofilms grew rapidly on the electrode, largely covering it after 45 hours. This growth was not uniform; the biofilm on the middle layer had significantly lower biovolume compared to the top and bottom layers, possibly because of low diffusion of substrate and the confining complexity of the 3D electrode.
Based on these findings, the researchers showed that thick biofilms are not beneficial for microbial fuel cell operations, and connectivity between cell clusters is very important for facilitating electron transfer. This is the first time that CLSM images are used to characterise biofilm formation on 3D carbon electrodes, and this study constitutes a key step for the future development of wider applications of EABs.
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